Masseter toxin is one of those treatments where patients ask two questions: will my face actually get slimmer, and will I lose the ability to chew. This study measured both. Published October 10, 2025 in BMC Oral Health, it was a quasi-experimental prospective trial in 24 healthy adults who received 50 units of botulinum toxin type A total, split bilaterally into the masseters. Lower-face volume was captured by 3D stereophotogrammetry at baseline, 4, 8, and 12 weeks, with satisfaction on FACE-Q and chewing assessed by a Chewing Function Questionnaire plus VAS.

Lower-face volume dropped significantly at every timepoint (p<0.05), and the effect kept building, with the largest reduction at week 12 rather than early on. FACE-Q satisfaction rose significantly after treatment. On the function side, there was no significant change in either objective or perceived chewing, and patients reported stable masticatory ability throughout. So a modest 25 units per side delivered visible jawline slimming with no measured cost to bite function.

The practical read: for lower-face contouring, roughly 25 units per masseter (50 total) is enough to reduce volume while keeping chewing intact, which gives you a straight answer for the patient who is nervous about bite strength. Just as useful for clinic flow, book the outcome review at about 12 weeks rather than 4. That is when the slimming is maximal, and reviewing too early risks a patient (and a clinician) thinking the dose underdelivered.

Source: BMC Oral Health (Vol 25, Issue 1, article 1595). https://pubmed.ncbi.nlm.nih.gov/41073980/